Syphilitic (luetic) interstitial keratitis

INTERSTITIAL KERATITIS
Interstitial keratitis denotes an inflammation of the corneal stroma without primary involvement of the epithelium or endothelium.

Causes. Its common causes are:
Congenital syphilis
Tuberculosis
Cogan's syndrome
Acquired syphilis
Trypanosomiasis
Malaria
Leprosy
Sarcoidosis

Syphilitic (luetic) interstitial keratitis
Syphilitic interstitial keratitis is associated more frequently (90 percent) with congenital
syphilis than the acquired syphilis. The disease is generally bilateral
in inherited syphilis and unilateral in acquired syphilis. In congenital syphilis, manifestations develop between 5-15 years of age.

Pathogenesis

It is now generally accepted that the disease is a manifestation of local antigen-antibody reaction. It is presumed that Treponema pallidum invades the cornea and sensitizes it during the period of its general diffusion throughout the body in the foetal stage. Later a small-scale fresh invasion by treponema or toxins excite the inflammation in the sensitized cornea. The inflammation is usually triggered by an injury or an operation on the eye.

Clinical features
Interstitial keratitis characteristically forms one of the late manifestations of congenital syphilis. Many a time it may be a part of Hutchinson's triad, which
includes: interstitial keratitis, Hutchinson's teeth and vestibular deafness.
The clinical picture of interstitial keratitis can be divided into three stages: initial progressive stage, florid stage and stage of regression.

1. Initial progressive stage. The disease begins with oedema of the endothelium and deeper stroma, secondary to anterior uveitis, as evidenced by the
presence of keratic precipitates (KPs). There is associated pain, lacrimation, photophobia, blepharospasm and circumcorneal injection followed by a diffuse corneal haze giving it a ground glass appearance. This stage lasts for about 2 weeks.

2. Florid stage. In this stage eye remains acutely inflamed. Deep vascularization of cornea, consisting of radial bundle of brush-like vessels develops. Since these vessels are covered by hazy cornea, they look dull reddish pink which is called 'Salmon patch appearance'. There is often a moderate degree of superficial vascularization. These vessels arising from
the terminal arches of conjunctival vessels, run a short distance over the cornea. These vessels and conjunctiva heap at the limbus in the form of epulit.
This stage lasts for about 2 months.

3. Stage of regression. The acute inflammation resolves with the progressive appearance of vascular invasion. Clearing of cornea is slow and begins from periphery and advances centrally. Resolution of the lesion leaves behind some opacities and ghost vessels. This stage may last for about 1 to 2 years.

Diagnosis
The diagnosis is usually evident from the clinical profile. A positive VDRL or Treponema pallidum immobilization test confirms the diagnosis.

Treatment
The treatment should include topical treatment for keratitis and systemic treatment for syphilis.
1. Local treatment. Topical corticosteroid drops e.g., dexamethasone 0.1% drops every 2-3 hours. As the condition is allergic in origin, corneal clearing occurs with steroids if started well in time and a useful vision is obtained.

• Atropine eye ointment 1 percent 2-3 times a day.
• Dark goggles to be used for photophobia.

2. Keratoplasty is required in cases where dense corneal opacities are left.
2. Systemic treatment
Penicillin in high doses should be started to prevent development of further syphilitic lesions. However, an early treatment of congenital syphilis usually does not prevent the onset of keratitis at a later stage. Systemic steroids may be added in refractory cases of keratitis.